Tire mold structure



` Sept 29, 1942- M. c. ovERMAN TIRE MOLD STRUCTURE 2I Sheets-Sheet loriginal Filed May 1o, 1939 l@ Q n NVENTOR Max C. Overmann ATTORNEYSept. 29, 19""1'21"4 M. c. ovERMAN TIRE Mouj STRUCTURE original Filedmay 10,'1939 2 Sheets-Sheet 2 ELS .mw w Y Dn U E E T mc/Mn PatentedSept. Z9, 1942 AUN'TED STATES PATENT d O FFICE 1 TIREMOLD STRUCTURE MaxC. Overman, New York, N. Y. v Original application May 10, 1939, lSerialNo.

272,826. Divided and this application 'December 6, 1939, Serial No.397,729

5 claims. (c1. lss-'38) This invention relates to a tire mold structureand is a division* of my c-pending application Serial No. 272,826, ledMay 10, 1939, now Patent 2,254,622.

In my co-pending' application Serial No. 248,185, I disclose an improvedform of tire having circumferentially extending ribs whichrarealternately draft and undercut in cross section. Besides the advantageof being substantially self-closing this structure lends itself to apleasing and novel color effect which I have originated and obtained byforming the undercut ribs of white rubber while forming the draft ribsas before of the black composition of the tire tread.

' I have found that no tire molds are available for making 'a tread withalternate draft and undercut ribs and as far as I am aware a moldstructure capable of forming my improved rib structure is broadly new.

In carrying out my invention I provide a tread rib mold comprising anumber of annular parts, divided into a number of circumferentialsections and having inwardly projecting rib spacing members. The annularparts of the tread rib mold assembly are secured together by detachablemeans such as nuts and bolts which preferably extend between annularsupport members provided on either side of the assembled annularmembers. The sections of the latter are detachably secured in theassembly so that each may be released and removed independently of othersections. The assembled tread rib mold may be'mounte'd in a tire mold inposition to engage the periphery of the tread of an unvulcanized tire.

Although the rib spacing members illustrated herein are inclined to oneanother to form alternate draft and undercut rib forming spaces they aredistributed between the annular mold parts in such a way that ribsinclined toward one another are not carried by the same annular part.Thus the sections of rib spacing members carried by the sections of theannular tread rib molds parts will not prevent any section of saidannular parts from being readily separated from the vulcanized tire.

Since in assembling my rib mold structure some of the rib forming spacesmay be readily filled with a special rubber composition, my moldstructure lends itself particularly to the formation of a treadstructure having ribs some of which are different in composition, incolor or otherwise, from the other ribs.

The invention will `best be understood if the d following description isread in connection with the accompanying drawings, in which:

Figure 1 is a transverse section through the tire mold assembly;

Figure 2 shows the rib mold assembly lying on one s'ide as viewed fromabove;

Figurey 3 is a detail View of a portion of the structure shown in.Figure 2 showing how the parts of the tread rib mold are superimposedone upon the other;

Figure 4 is a plan VView of the mold surface of the rib mold assembly;

Figure 5 is a detail perspective view showing the sections of theannular tread rib mold members being assembled upon the clamping bolts;

Figure '6 is av detail cross sectional view showing the parts of the ribmold being assembled, and one manner of applying rubber composition tofill the alternate, undercut rib forming spaces;

Figure 7 is a detail View showing how the draft ribs are formed in thespaces between the undercut ribs.

The rib' mold consists of the annular support members I and 9 and theintermediate annular m'old members 2, 3, 4, 5, 6, 1, and 8. Each ofthemold members 3, 4, 5, 6, and 1 has projecting inwardly from its innerperiphery two rib spacing members, a: and y, which constitute the sidewalls of the individual rib forming mold spaces. The rib spacing memberscarried by each of the mold members 3, 4, 5, 6, and 'l are inclinedoutwardly from each other thus forming between themselves mold spaces dadapted to'shape draft' r'ibs. It will be noted, however, that each ribspacing member of one annular mold `member is inclined inwardly towardthe nearest rib spacing member carried by the abutting annular moldmembers thus forming spaces u :adapted to shape ribs which are undercutin cross section, i. e., wider at the tread surface than' at the base.

Y YAnnular mold members 2 and 8 are provided with only one rib spacingmember each, a: and y respectively. They are inclined toward the nearestrib of the abutting mold members together with which they' provideundercut rib forming spaces, completing the alternate arrangement ofdraft and undercut rib forming spaces.

The support members I and 9 are preferably continuous unitary memberswhereas the mold members 2 to 8 inclusive are divided circumfer-'entially into a number` of sections. As illustrated (Fig. 2), they aredivided into siX sections a, b, c, d, e, f. Each section is providedwith two transverse bores t to receive a locking bolt and the supportmember 9 is correspondingly bored at similar distances. The supportmember I, as illustrated, is provided with a central bore II in itsinner face which is internally threaded to receive one end of bolt I0.In assembling the rib mold, bolts I may first be seated in bores II ofthe support I, after which the sections of mold member 2 are positionedby inserting the free ends of bolts I0 in the bores t and lowering thesections of member 2 until they are superimposed upon support member I,as indicated in Figure 5. The sections of annular mold member 3 are thenassembled'in the same way and so on until the assembly is complete. n

The sections of the mold members may be disassembled from the vulcanizedtire in the same manner, by first removing the retaining nuts IIIa andbolts I0 and then rst separating the sections of mold member 8 from theassembly, followed by the sections of mold member 1, and so on. Since nosection of any of the mold members carries sections of rib spacingmembers which are inclined toward one another, each section may bereadily separated from the vulcanized tire.

Where it is desired to ll some of the rib forming spaces with a ribforming composition different in color or in other respects from thatused for forming the other ribs it willbe convenient to ll the ribspaces which are to receive one kind of rib forming composition whilethe rib mold is being assembled. This may be accomplished by depositingsome of the desired composition on the opposingfaces of said rib spacingmembers before they are assembled in abutting relationship. In this Waythe rib spaces to be preliminarily filled will be filled and thematerial compacted when the adjoining mold members are moved laterallytogether, without the difficulty which would be encountered in trying toll the spaces through their open ends. In the drawings (Fig. 6) I haveindicated the spaces u for forming undercut ribs as being preliminarilyfilled with a special composition w, preferably colored white to give adistinctive appearance to the tread of the tire, while the various moldmembers are being assembled. In Fig. 7 I have shown the spaces d alsofilled with the rubber composition from the tread portion of the tire,which is accomplished when the unvulcanized tire is forced against theassembled rib mold surface in a manner well understood by those skilledin this art.

Each of the bolts is provided with a nut Illa to tighten the members Ito 9 together and secure them in position. The complete tread rib moldassembly is inserted within a tire mold comprising two complementaryparts I 2 and I3 adapted when brought together to form a closure toreceive an unvulcanized tire and shape it while it is being vulcanized.At intervals adjacent their peripheries the tire mold members I2 and I3are provided in their lip portions I2a and I3a with registering axiallyextending apertures I4 and I5 to receive dowel pins I6 by which the twotire mold members I 2 and I3 may be brought into register and securedtogether.

As illustrated herein the lip portions I 2a and I3a of tire mold membersI2 and I3 are formed so that when the tire mold is closed a space willbe left between the lip portions sufficient to receive lugs 5a providedat intervals projecting outwardly from the outer periphery of tread ribmold member 5. The lugs 5a are bored at 5b to receive the dowel pins I6.By positioning lugs 5a so that the bores 5b are in register withapertures I4 and I5 the mold members 5, and therefore the whole treadrib mold assembly will be centered and held in place by dowel pins I6.The tire mold members I2 and I 3 are shaped interiorly .to fit snuglyaround the tread rib mold assembly, which is thus supported adjacent theinner periphery of the tire mold.

The tire mold members I2 and I3 are formed with registering concavities2I to receive the valve member 29 attached to .the air core 2'I by thevalve head 30 and provided with nut 3| screw threadedly secured on theexterior of the valve member.v Valve 29 extends outwardly through thewall of the tire mold and at its free end has a reduced portion 32 forconnection with a source of fluid supply, such for example as thecompressed air hose of an hydraulic pot vulcanizer.

In the operation of the invention the tread rib mold is first assembledand then placed in one of the members I2 and I3 comprising the tiremold. An unvulcanized tire or carcass 23 which ordinarily comprises thefabric plies 24, the breaker strip 25, and `the tread 26, indicated inbroken lines in Figure 1, by way of example, is placed on one sidewithin the concavity provided in the tire mold member, with theperiphery of tread surface 26 adjacent the mold surface of the tread ribmold. The air core 27 is then inserted within the tire and, after thetread mold has been closed and dowel pins I6 inserted in place, pressuremay be applied to the unvulcanized tire 23, as by admitting fluid underpressure into core tube 2'I, thereby forcing the tread surface of theunvulcanized surface outwardly against the tread rib mold surfacecausing the rubber composition from the tread portion 26 to flow intothe unlled spaces provided between the rib spacing members a: and y. Inpractice, since the tire mold members I2 and I3 will ordinarily beheated to a high degree when the unvulcanized tire 23 is insertedtherein, the rubber composition from the tread portion 26 will tendimmediately to flow into the unlled spaces provided by the rib spacingmembers :z: and y, and this flow of rubber from the tread portion 26 isincreased when pressure is applied to expand the tire outwardly, as byadmitting uid pressure into the core tube 2'I. The step of vulcanizingtakes place of course after the rubber flows into the unfilled spacesfrom the tread portion 26 between spaces :r and y. In practise, ow ofthe rubber composition into the rib forming spaces, and the step ofvulcanizing, are performed substantially simultaneously since the stepof connecting valve member 29 to a source of uid pressure and the stepof vulcanizing are usually both performed in an hydraulic potvulcanizer.

To insure tight fitting of annular rib mold members 2 to 8 inclusivethese may be given a tongue and groove formation illustrated in Figure1.

To provide a means for escape of excess rubber composition from the tireforming spaces during the time when the unvulcanized tire is beingforced against the tread rib mold surface under pressure, rearwardlyextending vents I8 are provided in annular rib mold members 3 to 8communicating with the circumferentially extending groove I9 which atintervals is provided with concavities or catch-basins 20.

It will be understood that the invention is not limited to the detailsalone described, but that it comprehends broadly a multi-part tread ribing rib forming and spacing members, said ma--\ mold, and the method offorming the ribs of a tire, as defined in the claims.

What I claim is:

1. Apparatus for forming a tire tread with circumferential ribs,alternately relatively wide load supporting draft ribs and relativelynarrow undercut wiper ribs, comprising an annular tire mold having onits inner periphery a number of inwardly projecting rib forming andspacing members positioned to form alternately disposed draft andundercut ribs, said mold being subdivided both radially andcircumferentially into juxtaposed sections, circumferential jointsbetween said sections being positioned only between the members formingthe undercut ribs.

2. Apparatus for forming a tire tread with circumferential ribs,alternately relatively wide load supporting draft ribs and relativelynarrow undercut wiper ribs, comprising an annular tire mold having onits inner periphery a number of circumferentially sectional inwardlyprojecting rib forming and spacing members, alternately converging anddiverging toward the tread surface, only diverging members beingseparable from one another by means of a circumferential jointintersecting the Zone between such diverging members.

3. Apparatus for forming a tire tread with circumferential ribs,alternately relatively wide load supporting draft ribs and relativelynarrow undercut wiper ribs, comprising an annular tire mold formed insections adapted to be closed together and to enclose between them atread forming matrix and an unvulcanized tire body, said matrixcomprising a number of circumferentially sectional annular rings, twoouter rings, and between them inner rings, and having a number ofinwardly projecting mutually convergtrix being divided into sectionalrings in a manner such that each two members adapted to form betweenthem a wiper rib are attached to diiferent rings and each of the innerrings is adapted to shape a complete load supporting rib and only partof at least one wiper rib.

4. Apparatus for forming a tire tread with circumferential ribs,alternately relatively wide load supporting draft ribs and relativelynarrow undercut Wiper ribs, comprising an annular tire mold having onits inner periphery a number of sectional inwardly projecting ribforming and spacing members, adjacent members of said number alternatelyconverging and diverging toward the tread surface, the convergingmembers being permanently connected in a rigid manner, and the divergingmembers being separable by means of a joint provided therebetween.

5. Apparatus for forming a tire tread with crcumferential ribs,alternately relatively wide load supporting draft ribs and relativelynarrow undercut wiper ribs, comprising two half-mold members adapted tobe secured together, and a tread forming matrix, shaped to formalternate relatively wide load supporting draft ribs and relativelynarrower undercut wiper ribs, positioned between said mold members, saidmatrix consisting of a number of annular sections, said sections eachhaving at intervals transverse bores, registering with similartransverse bores of adjoining sections, and radial vents, leading fromthe inner periphery of said matrix and communicating with saidtransverse bores, said vents being positioned only in that portion ofthe matrix which is shaped to form said load bearing ribs.

MAX C. OVERMAN.

